The present invention relates to a trailer system and more particularly relates to a trailer which has a unique pneumatic suspension system which supports and levels the load and allows the trailer to xe2x80x9ckneelxe2x80x9d or lower to accommodate loading and unloading items from the trailer.
Trailers for towing such items as motorcycles behind a car, truck or recreational vehicle are well known. The common trailer design consists of a solid axle to which wheels are mounted on opposite ends of the axle. Springs are attached to the axle at the widest location. The forward spring attachment is rigidly secured to an outside frame member for fore-to-aft axle stability and is attached to a rigid frame mount by a flexible spring hanger at the rearward end of the frame member. The spring hanger compensates for the unequal distance aft of the front spring hanger to the axle mount when the spring is compressed. This differential can be lessened by lowering the front spring pivot point but this practice is generally avoided because it is a more complex and costly design and adds axle and deck weight that may offset any advantages gained.
Typically, two longitudinal frame members are joined by load-carrying, transverse frame members upon which is mounted the trailer deck. The deck, by necessity, is located above the axle the distance of the upward wheel travel plus the thickness of the deck and deck frame. It is not uncommon for trailers to have a deck positioned 6xe2x80x3 or so above the center of the axle. The entire weight of the load, deck, frame and springs bear on the axle, wheel and the supporting surface.
The conventional towing trailer, due to the requirement that the trailer handle or accommodate the largest load possible, is designed with a suspension spring stiffness designed to support the maximum load. With a trailer designed for a typical load of 2,000 pounds, it is common design practice to use suspension parts that have a load capacity of 3,000 pounds. Trailers utilizing this design have springs which are rigid at very low load levels, as for example 500 pounds, which rigidity effectively negates any load cushioning except for tire compression. As the load increases, the springs come into play and absorb more of the shock imposed by the travel surface. The best ride occurs when the load has caused the springs to flex approximately 50%. At this point, stability has been sacrificed for softness of ride because the loaded springs have lost their ability to rigidly maintain direction of the wheels. This often happens when the wheels pass over a sharp bump in the travel surface.
Upon encountering a bump in the roadway, conventional springs force the wheels to follow the roadway because of the mass of the load. Inertia causes the load to resist changes while the lower mass of the wheels, assisted by the stored energy in the springs, forces the wheels downwardly to contact the roadway. When this happens, the wheels will move rearwardly a slight distance, changing directions slightly due to the different length of the spring. Because the wheels are in contact with the roadway, this slight side way wheel force will load the spring with the energy that it has accumulated. The spring energy will dissipate through the frame mount and will tend to move the load sideways. The side motion is exacerbated upon encountering washboard roads resulting in trailer lateral or side way sway. Even on relatively smooth surfaces, a trailer can experience considerable sway if the load is displaced by any amount by the action of forces such as the wind moving the load relative to the axle.
Some newer trailer designs utilize a rubber tube inserted in a hollow axle with a center torsion bar attached to a crank supporting the wheel spindle. With designs of this type, the only way to obtain additional vertical wheel travel is to extend the length of the spindle crank. If this is done, the wheel spindle at the end of the longer arm can deflect from the forward travel direction upon side thrust loads also leading to sway.
While instability of conventional trailer designs is a problem as outlined above, there are also other problems. Conventional trailers are generally not conveniently storable because of their size and extending draw bar. Also, conventional trailers are often difficult to load or unload because of the elevation of the deck. For example, in some instances, it is difficult if not impossible, for a single individual to unload a heavy item such as a motorcycle from a trailer.
In view of the foregoing, there exists a need for an improved trailer system which is simple, reliable, rugged, stable in transit, safe and offers convenience when loading, unloading and storing.
The trailer of the present invention has a weight center point which is selected to stabilize the vehicle handling and to greatly reduce the potential for handling difficulties, particularly when encountering emergency traffic conditions and rough roads. The trailer frame includes a center channel which is designed to receive and support the widest motorcycle tire in conventional use today. The frame is one-piece construction extending the full length of the trailer and is the load-carrying backbone of the trailer. This design concentrates the maximum weight at the center of the trailer equidistant from each wheel. Extending equidistant from the weight center point are two lateral support members terminating in the wheel area. The top of each of these two vertical frames comprises a steel plate forming a reverse U-shaped channel which provides a support surface for the axle mounts and the suspension load-carrying components.
A pair of axles are provided and each consists of a rigid steel tube that is pivoted near the center of the trailer and mounted in resilient bushing mountings. These bushings provide lateral support as fore-aft bracings for the wheels as well as providing a pivot point for the suspension.
The trailer uses air cylinders or bladders as suspension springs affording optimum suspension stiffness for the load and also providing independent suspension at each wheel. The air cylinders or bladders are connected to a pneumatic air suspension system which provides self-leveling and also allows the operator to selectively vent the bladders to lower the trailer. Automatic leveling for uneven load compensation is provided by leveling valves in the air suspension system. The trailer is automatically leveled to the relative frame/axle height and the system will increase air pressure in the lower cylinder until a proper level is attained. The air suspension system maintains the trailer deck at a consistent height above the roadway. The trailer of the present invention uses the air suspension system to adjust to the weight of the load. The level of the trailer is maintained by the introduction of a volume of air into the air cylinders. Once the desired level has been achieved, no additional air is introduced so the load floats and the ride remains soft.
Because of the geometry and simplicity of the system, the system applies the side thrust of the wheel load to the center of the deck. There are no intermediate mechanical variations that can affect the alignment of the wheels and consequently sway is not induced.
The trailer of the present invention also includes a removable draw bar for ease of storage. The trailer is provided with dual receivers to which the tow bar may be attached for towing and removed for convenient or compact storage.
Another significant advantage of the present invention is that the system allows a person without assistance to load and unload heavy items such as heavy touring motorcycles such as the well-known Honda Goldwing. To lower the trailer, an air control valve is operated to place it in the xe2x80x9cdownxe2x80x9d position which will vent compressed air from the air cylinders to atmosphere allowing the trailer to lower or xe2x80x9ckneelxe2x80x9d to a position with the end of the center channel only a fraction of an inch above the ground and the deck only a few inches above the surface. The lowered position allows the user to easily load and unload articles and in this position, the user can roll a motorcycle onto or off the trailer. The trailer may also be provided with a filler section which can be removably inserted into the center channel so that a flat or planar deck is provided if required. When the trailer is loaded, the deck is raised by placing the control valve in the xe2x80x9cupxe2x80x9d position to elevate the trailer.
The invention also includes a fail-safe inhibitor which fail-safe system will maintain the trailer at an elevated position above the roadway surface in the event of a catastrophic failure of the air support system.